A function of extracting and tracking a moving object is realized in a system employing a surveillance camera. In this type of system, an alarm is outputted when a moving object (a suspicious person) is detected within a specified area in an image obtained from a surveillance camera. There has also been put into practical use a system furnished with a function of displaying the result of tracking for easy recognition by surveillance staff (see Non-Patent Document 1 listed below).
Image-based tracking processing is achieved, for example, by using the following methods: a pattern matching method in which a tracking pattern is set first and then the pattern is located within images; a method relying on detection of the position of a moving object based on an optical flow; and a method relying on tracking of a characteristic, such as color, of a subject.
Image processing-based technologies for extracting and tracking a moving object, which have originally been studied for the purposes of application in surveillance cameras and realization of robot vision, have recently started to find application in digital cameras for general consumers.
For example, there has been disclosed a method in which a specified subject is tracked and then, when a shutter release button is operated, a still image having a composition in which the subject is positioned in the center is produced by image clipping processing (see Non-Patent Document 2 listed below).
There has also been disclosed a method attempting to prevent a target subject from moving out of a shooting range during a moving-image shooting operation (see Patent Document 1 listed below). With this method, moving vector-based judgment is performed with respect to whether or not there is a possibility of a target subject moving out of a shooting range, and if it is judged that there is such a possibility, a warning is outputted.
Patent Document 1: JP-A-2007-88611
Non Patent Document 1: HAGA Tetsuji, et al., “Intruder Detection and Tracking Camera”, [online], August, 2004, Mitsubishi Electric Corporation, [searched on Jan. 25, 2008], Internet<URL:http://www.mitsubishielectric.co.jp/giho/0408/0408111.pdf>
Non Patent Document 2: CASIO, Exilim Full-Line Catalogue, “Auto-Framing Function (right bottom of page 4)”, [online], November, 2007,[searched on Jan. 25, 2008], Internet<URL:http://ftp.casio.co.jp/pub/exilim/jp/exilim.pdf>